Conventionally, a ladder shaped chassis frame is provided in a small truck or a vehicle called a “sport-utility vehicle (SUV)” as described in, e.g., Patent Documents 1 and 2. The chassis frame is formed in the ladder shape by a pair of right and left main frames (also called “side frames”) extending in a vehicle length direction (vehicle longitudinal direction) and a plurality of cross-members each connecting the main frames together.
Typically, in the foregoing vehicle, power of an engine arranged in an engine room positioned in a front part of the vehicle is transmitted to rear wheels through a transmission, a propeller shaft, and a rear differential gear unit. In the case of a four-wheel-drive vehicle (4WD vehicle), a power transfer unit is provided between the transmission and the propeller shaft, and output of the transmission is distributed to front and rear wheels through the power transfer unit.
In the foregoing 4WD vehicle, power is transmitted from the power transfer unit to the front wheels through a front wheel propeller shaft and a front differential gear unit. The front differential gear unit is attached to a front part of a chassis frame. In such a case, in order to reduce transmission of vibration of the front differential gear unit to the chassis frame, the front differential gear unit is elastically supported by the chassis frame through a plurality of mounts (typically three or four mounts) each including a cylindrical rubber bush and a central shaft penetrating the center (center hole) of the rubber bush. Each of the mounts is attached to a mount bracket provided on the chassis frame, and is supported by the mount bracket.